Amazon had already offered free cloud storage of any music purchased from its Amazon MP3 service, and includes 5GB of free storage for other music and files. But now anyone with at least a 20GB storage plan for $20 a year gets to upload as much MP3 or AAC music as they want to the service. (It also appears to work with the free one-year 20GB account that Amazon has given away to those who purchase an album from Amazon MP3.) Once uploaded, you can stream your music to a Mac, PC, or an Android phone using the Amazon Cloud Player software.

Amazon’s new service is more of a shot across the bow of Google Music Beta than it is a direct competitor of Apple’s upcoming iCloud. Google Music has the same upload-once, stream-anywhere model, but without the integration of Amazon’s MP3 store. Google Music is currently a free service, but getting in means requesting an invitation and waiting for Google to send it to you. (It took me two weeks.) iCloud, on the other hand, offers downloads of your purchased-from-iTunes music to multiple devices, and will work with your other music with the $25-a-year iTunes Match service, but doesn’t offer streaming—which could be an issue if you want to cram your 40GB library onto your 16GB iPod touch.

Amazon is calling this a limited time offer, however, so it may just be a taste of the candy Amazon will ask you to pay extra for in the future.

[Christopher Breen contributed to this story.]

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